Friday, November 30, 2012

Thirty years ago, the first spacecraft sent to explore the outer solar system started slowing unexpectedly. Now we finally know what happened

By VIKTOR T. TOTH, SLAVA G. TURYSHEV / DECEMBER 2012

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Viktor's Google+ post and Spinor.info blog alerted me to the Spectrum IEEE on line article he co-authored with Dr. Turyshev. Having met both and played a small part in providing some data on the health of the PN10-11 spacecraft, was interested seeing what was said. If I do say so myself, I think you will enjoy the Spectrum IEEE article.

Finding the Source of the Pioneer Anomaly

Thirty years ago, the first spacecraft sent to explore the outer solar system started slowing unexpectedly. Now we finally know what happened

By VIKTOR T. TOTH, SLAVA G. TURYSHEV / DECEMBER 2012

Some 40 years ago, a quarter-ton lump of circuits and sensors slipped Earth’s surly bonds, sped past the moon and Mars, and hurtled toward Jupiter. The probe, Pioneer 10, and its sister ship, Pioneer 11, which followed a year later, were true trailblazers. They gave humanity its first close-up glimpses of worlds beyond the solar system’s asteroid belt. They also left behind a mystery—one that has simultaneously baffled and inspired astrophysicists for years.

Like many puzzles, this one started out with just a small hint that something was amiss. Not long after Pioneer 10 and 11 had passed beyond the orbits of Jupiter and Saturn, their navigators began to notice something unexpected. Both spacecraft seemed to be slowing down more than controllers had predicted they would, as if some force were tugging them ever so subtly backward toward the sun.

The magnitude of this deceleration was minuscule, just one ten-billionth of the gravitational acceleration that we experience on Earth’s surface. Such a small effect didn’t seem out of place at first. It would have shown up as a simple correction, the sort that spacecraft navigators routinely apply to accommodate fuel leaks and other small, transient deviations in spacecraft behavior. No one would have blinked an eye if it hadn’t been for one troubling detail: For years, as the spacecraft sped deeper and deeper into space, that tiny discrepancy stuck around. And no one could figure out where it came from.

An article we wrote with Slava Turyshev about the Pioneer anomaly and its resolution, at the request of IEEE Spectrum, is now available online.

It was an interesting experience, working with a professional science journalist and her team. I have to admit that I did not previously appreciate the level of professionalism that is behind such a “members only” magazine.

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Disclaimer: I supported the Pioneer Missions at NASA Ames Research Center with contractors for about 20 years starting back in 1983 as Pioneer 10 left the Solar System. (A year and a half break between missions, working with Lam Research.)

Seeing TV crews zero in on a small, 11 inch, B/W monitor showing Black or White checkerboard squares representing the one's and zero's of the data on June 13, 1983 of PN10 on its way towards the Taurus constellation sort of sticks in your memory. Hearing those one's and zero's turned into two different tones made by a BASIC program on a Commodore VIC-20 for 'Sounds of Pioneer' sort helps date me. :-)

Also Viktor hosts my old,old website. The thought of having a place to re-fly the Pioneer missions was even considered, but I couldn't find the 9 days of data around PN-10's encounter with Jupiter, December 3, 1973.

PIONEER 10 SPACECRAFT SENDS LAST SIGNAL - After more than 30 years, it appears the venerable Pioneer 10 spacecraft has sent its last signal to Earth. Pioneer's last, very weak signal was received on 23 January 2003. NASA engineers report that Pioneer 10's radioisotope power source has decayed, and it may not have enough power to send additional transmissions to Earth. NASA's Deep Space Network (DSN) did not detect a signal during a contact attempt on 7 February 2003. The previous three contacts, including the 23 January signal, were very faint, with no telemetry received. The last time a Pioneer 10 contact returned telemetry data was 27 April 2002.